1. Field of the Invention
The present invention relates to a wiring substrate such as a flexure that provides a head suspension incorporated in a hard disk drive with wiring.
2. Description of Related Art
Due to the widely spreading Internet and surging information, recent personal computers are required to process a large amount of data at high speed and hard disk drives incorporated in the personal computers are required to increase storage capacity and data transmission speed. Accordingly, a head suspension to write and read data to and from a disk in the hard disk drive must employ a highly functional flexure.
The flexure generally includes read wiring, write wiring, and a terminal on a tail part to be connected to a main circuit board.
To connect the terminal of the flexure to the main circuit board, there are roughly two techniques. One technique forms flying leads at the terminal of the flexure and joins the flying leads to external terminal pads of the main circuit board with the use of ultrasonic bonding. The other technique forms pads at the terminal of the flexure and joins the pads to the external terminal pads of the main circuit board with the use of a conductive bonding material.
In the case of the flying leads, an opening is formed in an insulating layer of the flexure, to partly expose the top and bottom faces of the read and write wiring embedded in the insulating layer. The exposed sections of the read and write wiring serve as the flying leads that are joined to the external terminal pads of the main circuit board with the use of ultrasonic bonding.
The flying leads are thin and narrow, and therefore, are low in physical strength. To enhance the strength of the flying leads, Japanese Unexamined Patent Application Publication No. 2003-31915 discloses a technique of providing the flying leads with a wide reinforcing section.
Simply providing the flying lead with the wide reinforcing section may prevent a break of the flying lead but may deteriorate the extensibility of the flying lead and decrease reliability of bonding such as bonding strength and connectivity when the flying lead is joined to an external terminal of an external circuit board with ultrasonic bonding.
This problem results in limiting the width of the wide reinforcing section provided for the flying lead. Therefore, the flying lead may twist to deteriorate reliability of bonding between the flying lead and the external terminal to which the flying lead is joined with ultrasonic bonding.